BRADEN CH280 Installation Maintenance And Service Manual page 38

BRAKE VALVE OPENING PRESSURE TEST
Whenever brake components are replaced or a brake
component malfunctions or fails, the entire brake system
should be inspected and tested. Your testing must include
checking the brake valve opening pressure in addition to a
thorough inspection of the failed components.
Preparation
Begin the inspection by verifying that the brake valve and
motor piping is correct for this application. If you are not
certain, contact your nearest BRADEN distributor, the
crane OEM, or the BRADEN factory Product Support De-
partment before proceeding. Do not attempt repairs on
equipment you are not familiar with. Fully remove the load
from the hoist and block or secure any moveable parts
of the crane or hoist before proceeding with brake valve
test. It will be necessary to lower the hook block or ball to
the ground (deck) because the brake will be completely
released. Make certain the test area is clear of all unau-
thorized personnel as the hoist will be operated in raise
and lower functions.
Brake Valve Pressure Test
1. Shut off the engine or motor driving the hydraulic sys-
tem and vent residual pressure as recommended by
the crane OEM.
2. Install an accurate 0–2,000 PSI (0–138 bar) pressure
gauge teed into the brake release line, located at the
lowering (nonbrake valve) side of the hydraulic motor.
This is typically a -4 JIC connection.
3. To eliminate the slight drag effect of the internal multi-
disc brake, remove the brake release line from the hoist
brake port and install a plug in the line or close to the
needle valve if so equipped.
4. To the internal brake port, install a hand pump with an
accurate 0–2,000 PSI (0–138 bar) gauge. Operate the
hand pump and apply approximately 1,000 PSI (69
bar) to the brake port to fully release the brake. Close
the hand pump valve to hold the brake released during
the remainder of the test.
5. Operate the crane power source at full throttle and
VERY slowly move the hoist control lever toward the
lowering direction while monitoring the brake valve
opening pressure. Record the pressure when the cable
drum begins to turn in the lowering direction.
6. The initial lowering pressure should be no lower than
575 PSI for the 1.5-inch BRADEN brake valve, Part
Number 81609 which is used on most single-speed
motors on CH165A and CH230B planetary hoists.
If the initial lowering pressure is less than the specification
listed the brake valve should be adjusted.
ADJUSTMENT OF BRAKE VALVE
1. Inspect the main spool spring to make certain it is not
damaged. If the spring is in good condition, the brake
valve opening pressure should be adjusted by install-
ing shims between the spring retainer (Item 3) and the
main piston spring. A maximum of .062-inch (1.6 mm)
shims are allowed in the 1.5-inch valves. Additional
shims may result in accelerated spring failure because
of overcompensation.
2. If the spring requires more than the maximum num-
ber of shims listed above to achieve the recommended
opening pressure, the spring should be replaced.
3. Inspect the brake valve piston and damper piston for
scoring and seal ring condition. The seal rings should
be replaced following disassembly and inspection. If
there is any scoring of the pistons and/or the brake
valve housing, the entire brake valve must be replaced.
4. Inspect the check valve poppet and seat for irregular
wear or damage. It the poppet set is damaged, the en-
tire brake valve must be replaced. Tighten the spring
retainers to 40 lb.-ft. torque.
NOTE: Always recheck the brake operation following in-
spection or adjustment, prior to placing the hoist back in
service.
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